There’s a good chance hip adduction doesn’t steal the show in your workouts. (The hip adduction machine is the one where you sit down and bring your legs together like you’re trying to pop a balloon between your thighs.)

But your adductors—the muscles running from the inside of your knees up to your groin—are more important than you might think, playing a crucial role in squat performance and even the health of your lower back.

In the video below, Kelly Starrett, author of Becoming a Supple Leopard and creator of MobilityWOD.com, demonstrates the adductor smash—a simple technique to help you improve the health and mobility of your adductors with nothing more than a kettlebell.